Antibody mimicking the action of RAS proteins on yeast adenylyl cyclase: implication for RAS-effector interaction.

Polyclonal antisera were raised against various subregions of Saccharomyces cerevisiae adenylyl cyclase in order to examine the molecular mechanism of interaction between adenylyl cyclase and RAS proteins. One of the antisera was found to activate adenylyl cyclase to an extent comparable to that activated by saturating amounts of yeast RAS2 protein produced in Escherichia coli. The stimulatory effect of this antiserum was shown to be additive with RAS2 protein when both antisera and RAS2 protein were present at low concentrations. At saturating amounts of RAS2 protein, the antisera did not exhibit additional stimulatory effects, suggesting that the actions of RAS2 protein and the antisera are complementary with each other. The antigenic determinant for the antibody involved in the activation was mapped to a 14-amino-acid segment, 1452-NSVDNGADVANLSY-1465, located between the leucine-rich repeats and the catalytic domain of adenylyl cyclase. Certain missense mutations affecting this 14-amino acid segment significantly reduced the response of adenylyl cyclase to both activating antibody and RAS proteins. These results suggest that this segment of adenylyl cyclase is intimately involved in the mechanism by which RAS proteins activate this downstream effector.     

Mapping of replication initiation site in Mycoplasma capricolum genome by two-dimensional gel-electrophoretic analysis.

The homolog of the dnaA gene, which has been reported to be present in the vicinity of the initiation site of replication in the genome of Mycoplasma capricolum (M.Miyata, L.Wang, and T.Fukumura, J. Bacteriol. 175: 655-660, 1993) was mapped precisely. A 9540-bp region containing the dnaA gene was cloned and the entire region was sequenced with the exception of a previously reported region of 2517 bp (Fujita, M.Q., Yoshikawa, H. and Ogasawara, N. Gene 93: 73-78, 1992). The organization of the 9540-bp region was compared with that of corresponding regions in other bacteria. The arrangement and directions of rnpA, rpmH, dnaA, dnaN were conserved, but no other open reading frames were found that were homologous to those that are commonly found around dnaA genes in other bacteria. The directions of movement of the replication fork around the dnaA gene were analyzed by neutral/alkaline two-dimensional gel electrophoresis. The forks developed in a 1569-bp region that consisted of the dnaA structural gene and its downstream non-coding region, and then they proceeded bidirectionally.     

Cigarette smoking during pregnancy lowers aromatase cytochrome P-450 in the human placenta

To clarify whether cigarette smoking during pregnancy causes an organic alteration in placental estrogen producing ability, we determined the catalytic activity of aromatase by the tritiated water assay, and tissue level of aromatase cytochrome P-450 (P-450_arom) by the specific enzyme-linked immunosorbent assay, in placental samples from nonsmokers and smokers. As pregnancy progressed, both aromatase activity and P-450_arom concentration increased in placentas from nonsmokers and smokers. However, the gradient of the increase was significantly less in heavy smokers (20 cigarettes a day) than in normal and moderate smokers (<20 cigarettes a day). At term, the mean aromatase activity and P-450_arom concentration in placentas from heavy smokers were significantly lower than in nonsmokers and moderate smokers, while aromatase activity per P-450_arom (turnover rate) and the mean placental weight were comparable among the three groups. In contrast, the ratio of aryl hydrocarbon hydroxylase activity to aromatase activity was higher in placentas from heavy smokers. Immunohistochemical studies showed that P-450_arom was localized in the cytoplasm of syncytiotrophoblasts of chorionic villi in placentas from both nonsmokers and smokers. These results suggest that the induction of placental P-450_arom during gestation is suppressed by maternal smoking, resulting in a reduction in estrogen producing ability, while placental xenobiotic P-450 is induced.     

Nucleotide sequences recognized by the AGAMOUS MADS domain of Arabidopsis thaliana in vitro

The AGAMOUS gene of Arabidopsis thaliana is a homeotic gene involved in the development of stamens and carpels. This gene encodes a putative DNA-binding protein sharing a homologous region with the DNA-binding domains, MADS boxes, of yeast MCM1 and mammalian SRF. To examine the DNA-binding activity of the AGAMOUS protein, double-stranded oligonucleotides with random sequences of 40 bp in the central region were synthesized and mixed with the AGAMOUS MADS domain overproduced in Escherichia coli . Oligonucleotides which bound to the MADS domain were recovered by repeated immunoprecipitation with an antibody which recognizes the overproduced protein. From a comparison of the recovered DNA sequences, the consensus sequence of the high-affinity binding-sites for the AGAMOUS MADS domain was determined to be 5'-TT(A/T/G) CC(A/T)₆GG(A/T/C)AA-3'. DNase I footprinting and methylation interference experiments showed that the MADS domain binds to this motif. Comparisons with the binding-site sequences of other MADS-box proteins revealed that the MCM1 binding-sites in a-mating type-specific promoters of Saccharomyces cerevisiae show similarities with the binding-site sequence of the AGAMOUS MADS domain. A synthetic MCM1 binding-site in the upstream region of the STE2 gene is recognized by the AGAMOUS MADS domain.     

Augmentation of antitumor immunity in regional lymph nodes by local immunotherapy

We have previously reported that the antitumor effect of OK-432, a streptococcal preparation, is markedly augmented when injected intratumorally together with fibrinogen (OK-432/fbg) [1]. In order to elucidate the effects of this immunotherapy on regional lymph nodes (RLN), we carried out both morphological and functional analyses of the RLN from colonic cancer patients treated with OK-432/ fbg. Computer-aided morphometry revealed that the maximal cross-sectional areas and the broadest diameters of the RLN were significantly greater (p<0.01) in patients who had undergone local immunotherapy than in patients who had not. The component structures of RLN, such as sinus, follicle and paracortex, were all enlarged in the OK-432/fbg-treated patients, and necrosis of metastatic tumors was observed. RLN lymphocytes recovered from OK-432/fbg treated patients showed elevated reactivity to phytohemagglutinin (PHA) and the stimulation index was clearly higher than that of control patients. Flow cytometric analysis revealed a predominance of T-cells, especially CD4 subsets, and higher positivity for both CD25 and HLA-DR. Furthermore, RLN lymphocytes killed more effectively K562 and Daudi cells in the patients who had had immunotherapy. These results suggest that the effect of local immunotherapy with OK-432/fbg is not restricted to the site of injection but extends to the lymph nodes, and contributes to tumor regression through the augmentation of cellular immunity.Abbreviations RLN regional lymph node(s) - OK-432/fbg OK-432/fibrinogen solution - PHA phytohemagglutinin - NK natural killer - LAK lymphocyte activated killer     

Expression and Promoter Activity of Genes for Isozymes of Horseradish Peroxidase

The expression and promoter activity of genes for isozymes ofhorseradish peroxidase, namely, prxCla, prxClb, prxC2 and prxC3,were studied. Organ-specific expression of these genes in horseradishplants was examined by Northern blot analysis. The group ofprxCl genes was expressed mostly in stems, while prxC2 and prxC3were expressed to a greater extent in roots. Hardly any expressionof any of the genes was detected in leaves. In transient-expressionassays with tobacco protoplasts, about 500 bp of the 5'-noncodingregions of each of the genes, ligated to the gene for ß-glucuronidase(GUS), exhibited significant promoter activity. In particular,the fragments extending from the initiation codon of the prxC2gene to –529 bp and –1 kbp supported high levelsof GUS activity, which were 4.4 and 11.4 times respectively,the activity observed under control of the 35S promoter fromcauliflower mosaic virus (CaMV). Conserved enhancer sequencesof human genes were found in the 5'-flanking region of prxC2,and deletion of the regions that contained the enhancer sequencesreduced the GUS activity. High levels of GUS activity were observedin transgenic tobacco plants that contained 1 kbp of the 5'flanking region of prxC2 fused to the GUS gene. GUS activitywas diminished when deletion from the 5' end extended as faras the CAAT box. No significant organ-specific expression ofGUS was observed with any such deletion. (Received April 15, 1992; Accepted September 11, 1992)     

Characterization and mapping of Ds—GUS-T-DNA lines for targeted insertional mutagenesis

The transposition patterns of the Ds —GUS transposon T-DNA in 23 independent single-copy lines have been characterized and the map positions of 10 of them on three of the five Arabidopsis chromosomes are reported. Using overexpressed Activator ( Ac ) elements as a transposase source, it was found that the primary determinant of transposition frequency is the insertion site of the Ac -T-DNA. Neither the structure of the transposon T-DNA nor, in most cases, its insertion site have a significant effect on transposition frequency. Both the frequency and timing of transposition are influenced by the parent through which the transposon and transposase T-DNAs are transmitted. Overall, nearly 75% of plants in which excision has occurred bear a reinserted element and very short-range transpositions predominate, underlining the advantage of using mapped transposons for insertional mutagenesis.     

Accumulation of poly-(hydroxybutyrate) by a non-sulfur photosynthetic bacterium,Rhodobacter sphaeroides RV at different pH

Summary Effect of pH of culture media on intracellular accumulation of poly-(hydroxybutyrate) (PHB) by a non-sulfur photosynthetic bacterium, Rhodobacter sphaeroides strain RV was studied in pH-stat cultures. Sub-optimal pH for growth, 8.0 or 8.5 gave the higher content of PHB rather than optimal pH 7.5 for growth. These results show that growth and PHB accumulation of the bacteria can be controlled by pH of culture media.     

Water Soluble Pigments Containing Xylose and Glucose in Gametangia of the Green Alga, Bryopsis maxima

Several water-soluble pigments were purified from gametangiaof Bryopsis maxima by liquid chromatography and characterizedby pyridylamination and high-performance anion-exchange chromatography.The structure of the main red pigment is proposed based on thedata of infrared spectrum, Mass spectrum, ¹H and ¹³C NMR spectraand pyridylamino analysis. As a consequence, this pigment containeda tetrapyrrole with phytol and a sugar chain comprised of xyloseand glucose. The sequence of the sugars in the chain was determinedbased on its Mass spectrum. The pigment was similar to chlorophyll-originpigments observed in other plants. No aldehyde group, however,was present at C5 in the open tetrapyrrole chain. (Received August 3, 1994; Accepted November 10, 1994)